slides?

[mpukita]

I've read the analysis, and I'd buy the static erg vs. boat comparison analysis ... because the boat keeps moving forward, even as one recovers. But with the slides, the entire mass of the machine must come to a stop, and be moved forward again, if there is any movement from dead center, so I would postulate that it's not a direct comparison to look at the boat as being synonymous to the erg on slides. It's simply not a pure (or even close?) model of what the boat is doing. It seems to me the physics is (much?) different.

[johnlvs2run]

The bungees automatically toss the erg back in the other direction each time, saving additional energy.

[PaulH]

By heavyweights I am referring to those who are 200 to 250 pounds or so.

Why "or so" - if the relationship is linear then the heavier the rower, the more they'll benefit. Presumably a 500lb rower would gain around 12 seconds?

Many women are around 100 to 110 pounds so, no, they would not be automatically considered to be 250 pound male heavyweights. Lightweight for women is 135 pounds or less.

That's right, so heavyweight is 136 or more. That's why it's important to be precise, as you have now corrected yourself to be. It's not 3-6 seconds for heavyweights, as you initially and incorrectly summarised, but (allegedly) 3-6 seconds for men between approximately 200lbs and 250lbs.

The slide advantage increases, as the difference between the weight of the rower and the rowing machine likewise increases.

So the evidence that lightweights lose out is wrong, but the evidence that heavyweights gain is right? On what basis do you make that assumption?

Cheers, Paul

[johnlvs2run]

Why "or so"

Heavyweights.

if the relationship is linear then the heavier the rower, the more they'll benefit.

Right.

Presumably a 500lb rower would gain around 12 seconds?

If the slides would hold that much weight and still function.

so heavyweight is 136 or more.

Yes, that's right.

That's why it's important to be precise, as you have now corrected yourself to be.

Thank you for saying that John Rupp is precise.

It's not 3-6 seconds for heavyweights

Well it might be 3 seconds for lightweights.

It's already 1.5 to 3 seconds for me, and would be much more than this for a heavyweight, depending on how much excess weight they were carrying. For a heavy heavyweight it could be 7 seconds or more.

So the evidence that lightweights lose out is wrong

Yes that assumption would be wrong.

Most lightweights will also be faster on slides, with the possible exception of very light women.

the evidence that heavyweights gain is right?

Yes all heavyweights should be much faster on the slides.

On what basis do you make that assumption?

Heavyweights are heavier.

This is not an assumption, but an observation that most people are able to see.

[PaulH]

You didn't answer the question - some evidence, from the same study, suggests that on slides heavyweights go faster but lightweights go slower. What did the study do wrong that gave it (according to you) a result that is half right and half wrong?

[PaulH]

Oh, I forgot

Thank you for saying that John Rupp is precise.

You know that precise has nothing to do with correctness. For example, to say that you weigh 98.38593288594kg would be both extremely precise and very wrong.

[johnlvs2run]

Wow, Paul that's great... I have both of them right.

[PaulH]

You still didn't answer the question.

[johnlvs2run]

PaulH,

Just for you, I took a look at the study and here are a couple of quotations from it.

"in the static (ergometer) you are actually performing more work in accelerating your body weight than in the dynamic (floating) case where the work is split between accelerating the boat and your body in opposite directions."

"on a static erg, the rower is required to put in six times as much energy accelerating/decelerating just their bodyweight, compared to a boat or a dynamic erg where the energy is split between the bodyweight and the boat/erg."

I hope this answers your question.

[johnlvs2run]

Thus the study has come to the same conclusions that I have.

[johnlvs2run]

A couple more quotations from the study:

"Cas Rekers (designer of the Rowperfect) has performed tests comparing the `indicated' power output with and without the flywheel fixed - the subject gained about 10-20% power output in the second case, representing the additional power that could be applied to the flywheel instead of accelerating the bodyweight."

"More energy is used up by accelerating just the body backwards and forwards than by accelerating the body + (lighter) boat/erg in opposite directions."

[PaulH]

PaulH,

Just for you, I took a look at the study and here are a couple of quotations from it.

"in the static (ergometer) you are actually performing more work in accelerating your body weight than in the dynamic (floating) case where the work is split between accelerating the boat and your body in opposite directions."

"on a static erg, the rower is required to put in six times as much energy accelerating/decelerating just their bodyweight, compared to a boat or a dynamic erg where the energy is split between the bodyweight and the boat/erg."

I hope this answers your question.

Fascinating - you're quoting from the physics of ergs page (http://www.atm.ox.ac.uk/rowing/physics/ ... #section12), which says nothing about the study of athletes that you appeared to be attempting to sum up (in fact the link wasn't even provided until after your summation). The actual study apparently shows, amongst other things, that "in the lighter categories (male and female) the performance (making allowances for fatigue) was negative."

So, again, why did that study get the answer 'right' for heavyweights, but 'wrong' for lightweights?

Or, if you prefer, why does the physics page have it 'right' about slides, but 'wrong' when it says "anyone moving up from sea level and trying a long-distance erg would probably find their power reduced by 20% (or times increased by approximately 7%)"?

I'll take an answer to either question, so long as it's more substantial than "because I say so".

[johnlvs2run]

the link wasn't even provided until after your summation

Yes that's amazing, we came to the same conclusions independently.

Actually though I came to these same conclusions a few years ago.

[PaulH]

You still didn't answer either question

[johnlvs2run]

Paul,

The benefits of the slides are not dependent on your understanding of them.